Apparatus for manufacturing steel sheets with layers of protective metal

ABSTRACT

Apparatus manufacturing a steel sheet coated with a layer of protective metal wherein a powder of the metal is coated on the surface of the steel sheet and the coated steel sheet is dried and then rolled by means of a rolling mill to form a layer of the protective metal bonded to the surface of the steel sheet, a small quantity of atomized oil is electrostatically applied onto the surfaces of the rolls of the rolling mill and the applied oil is treated with equalizing rolls to form thin oil films of uniform thickness on the surfaces of the rolls whereby to prevent the powder of metal from adhering to the surfaces of the rolls.

United States Patent Yamagishi et al. Nov. 5, 1974 APPARATUS FORMANUFACTURING 2.107.541 2/193s Longm; 72/236 STEEL SHEETS WITH LAYERS 0Fgoehrirzg l 9 29/420 rasser PROTECTIVE METAL 2,764,508 9/1956 Feickll7/93.4 R [75] Inventors: Hidehisa Yamagishi; Fumitoshi 3,478.843ll/l969 Eckardt 184/626 Yokoi, both of Kawasaki Japan 3,648,497 3/1972Long Cl Z1] 72/236 3,661,612 5/1972 Jackson et a]. 117 31 [73] Assignee:Nippon Kokan Kabushiki Kaisha,

Kamagawaken Japan Primary Examiner-C. W. Lanham [22] Filed: July 31,1973 Assistant ExaminerE. M. Combs [21] Appl' NOJ 384,384 Attorney,Agent, or Firm-Flynn & Frishauf Related US. Application Data [57]ABSTRACT [62] Division of Ser, N01 259,287, June 2, 1972, Pat. No.

3,781,968. Apparatus manufacturing a steel sheet coated with a layer ofprotective metal wherein a powder of the [30] Foreign ApplicationPriority Data metal is coated on the surface of the steel sheet and June16,1971 Japan 46-42498 the Coated Steel Sheet is dried and rolled bymeans of a rolling mill to form a layer of the protec- 52 us. c1 29/420,72/45, 72/236 five metal bonded the Surface of the Steel Sheet a 5 IL 01322f 1321b 45 m 1321b 27/06 small quantity of atomized oil iselectrostatically ap- [58] Fie|d f Search 29/42() 4205; 72/41, 43, pliedonto the surfaces of the rolls of the rolling mill 72/44, 5 117/31 934,9343; 184/626 and the applied oil is treated with equalizing rolls toform thin oil films of uniform thickness on the sur- 5 References Citedfaces of the rolls whereby to prevent the powder of UNITED STATESPATENTS metal from adhering to the surfaces of the rolls.

l,634.258 7/l927 Halpin 72/43 9 Claims, 4 Drawing Figures APPARATUS FORMANUFACTURING STEEL SHEETS WITH LAYERS OF PROTECTIVE METAL This is adivision, of application Ser. No. 259,287, filed June 2, 1972, now US.Pat. No. 3,781,968.

BACKGROUND OF THE INVENTION This invention relates to apparatus formanufacturing a steel sheet coated with a protective metal, aluminum forexample, by applying, a powder of the metal upon the surface of thesteel sheet and then rolling the coated steel sheet, and moreparticularly relates to an apparatus for preventing the powder of themetal from adhering to the surface of rolls of the rolling mill.

Steel sheets are often coated with a powder of alumi-. num and then thecoated steel sheets continuously pass through a rolling mill. In such acase, the rolls of the mill should, desirably have clean and drysurfaces. However, the cleaner the roll surfaces are, the more aluminumpowder tends to adhere. Although oil films formed on the surfaces of therolls are effective to prevent the aluminum powder from adhering to theroll surfaces, the coating of the aluminum powder before rolling iseasily permeated by oil, so that the quantity of the oil applied ontothe roll surfaces should be small. If the quantity of the oil isexcessive, for example more than 50 mg/m the aluminum powder tends toadhere to the rolls as if no oil film were formed thereon.

SUMMARY OF THE INVENTION It is an object of this invention to providean-improved apparatus for preventing the metal powder from adhering tothe surfaces of the rolls of the rolling mill whereby to manufacture asteel sheet coated with a layer of protective metal firmly bondedthereto and having a beautiful finished surface.

According to the present invention there is provided an apparatus formanufacturing a steel sheet coated with a layer of protective metalcomprising a rolling mill including cooperating rolls between which asteel sheet coated with a powder of the protective metal is passed,means for electrostatically applying a small quantity of oil onto thesurfaces of the rolls, and equalizing rolls cooperating with the rollsof the rolling mill for forming thin films of the oil on the surfaces ofthe rolls of the rolling mill.

BRIEF DESCRIPTION OF THE DRAWING FIG. 4 is a cross-sectional view of thenozzle shown in FIG. 3 taken along a line IV--- IV. I

DESCRIPTION OF THE PREFERRED QPl ENT With reference to FIG. 1 of theaccompanying-drawing, a steel sheet 1 coated with layers 2 of a powderof aluminum is rolled by passing it through the pair of rolls 3 of a linsmjlltqfarrnj s i sbsetha inssni tm aluminum layers 7. Whenthesurfaces of the rolls 3 are I clean and dry, the powder of aluminumtends to adhere on the surfaces of the rolls. The powder of the aluminumadhering on the rolls with small bonding force can be readily removed bymeans of a doctor knife 6, for example, but those firmly adhering cannot be readily removed. I

For this reason, it has been the practice to apply oil onto the surfacesof the rolls by means of oiling devices 5 and then forming uniform oilfilms by means of equalizing rolls 4. The quantity of the applied oilshould be in a range of from 5 mg/m to 50mg/m When the quantity of theoil is less than 5 mg/m aluminum powder tends to adhere to the surfacesof the rolls, whereas when the quantity of the oil exceeds 50 mg/m theoil permeates through the aluminum powder to reach the surface of steelsheet thereby decreasing the adhesiveness at the Al/Fe interface andcausing the aluminum Lewd?! I9 adhere $99 syr aq aqtths. r9112- a Thedetail of the oiling device is shown in FIG. 2. Oil 9 in an atomizingtank 8 is atomized by the primary pressurized air 10 ejected from anozzle 11 and the concentration of the atomized oil is adjusted by thesecondary air admitted into the atomizing tank 8. The atomized oil isthen ejected toward roll 3 through the slit 14 of a double walled nozzle13. In front of the nozzle 13 is positioned an electrode 15 for ionizingthe atomized oil ejected from slit 14. A source of high voltage power,not shown, is connected between the electrode 15 and roll 3 for causingthe atomized oil to be charged at the electrode 15 and attached to theroll which is earthed to form a thin oil film on the surface of theroll.

FIGS. 3 and 4 show a modified nozzle 13 comprising concentric tubes 13aand 13b. The outer tube 13a has an elongated slit l4 and theinner tube13b is connected with the atomizing chamber 8 through a pipe 16 and isprovided with a slit 13c in parallel with a slit 14 but on the oppositeside. The electrode may be provided in pipe 16 as at 15' as shown inFIG. 2.

The oil used may be a natural oil, such as cottonseed oil, or asynthetic oil such as .dioctyl sebacate. However, mill oil of theaqueous emulsion type can also be .useds.

The equalizing rolls 4 may be made of felt, nonwoven synthetic fiberfabric or rubber. When made of metal, the doctor knife '6 not onlyremoves the aluminum powder adhered to the r0113 but also serves as thegrounding terminal of the roll. However, when the roll is grounded byanother means, the doctor knife is not ne es a ily..l2q mal 9t'mtal.-.--m" The adjustment of the quantity of-the applied oil can be accomplishedby varyingthe flow of the secondary air while maintaining the pressureof the primary or atomizing air at a definite value. Since the adequatequantity of the secondary air varies dependent upon the type of the usedoil, it is advantageous to plot calibration curves for respective oils.

V V EXAMPLE W Oil films were formed under following conditions whenaluminum layers having a thickness of 30 microns were formed by rollingon the surface of steel strips having a thickness of Q.8 mm.

Quantity Primary of se- Electro- Material Quantity air condary static ofequaof oil pressure air voltage lizing applied Example Kg/cm OilNm"'/min V roll mg/m l l dioctyl 2 40.000 felt sebacate 2 3.0 do. 6 do.do. 50 3 0.7 Cottonseed 6 do. nonwoven oil nylon fabric 4 1,5 t. 6 do.d0. 50 s 0.7 30% aqueous 5 do. nonwoven 20 emulsion of tetron* rayon oil6 1.0 do. 6 do. do. 50

' Trademark In examples I, 3 and 5 no aluminum powder adhered to thesurfaces of the rolls and it was possible to continuously manufacturealuminized steel sheets having beautiful surface finish without thenecessity of using the doctor knife.

ln the cases of Examples 2, 4 and 6, however, since the quantity of theapplied oil have exceeded the upper limit, aluminum powder often adheredto the surfaces of the rolls. However, it was possible to readily removethe powder with the doctor knife because the powder is adhering with asmall bonding force, thus causing no trouble for the continuousproduction.

According to this invention, since the rolling oil is electrostaticallyapplied to the rollers it is possible to improve the efficiency ofutilization of the oil and to minimize the quantity of the applied oilso that post treatment of degreasing is not necessary. Moreover, as thequantity of the applied oil is small, adhesion of the metal powder tothe roll surface can be effectively prevented, thus assuring continuousrolling of metal coated steel plates having a beautiful surface finish.

While the invention has been shown and described in terms of specificembodiments, it will be clear that many changes and modifications may bemade without departing from the scope of the invention. For example,instead of atomizing the oil by pressurized air and then conveying theatomized oil onto the surfaces of the rolls by electrostatic force it isalso possible to atomize the oil and then convey the atomized oil by thesame electrostatic field as is well known in the art of electrostaticcoating.

What is claimed is:

1. Apparatus for manufacturing a steel sheet coated with a layer ofprotective metal comprising a rolling mill including:

cooperating rolls between which a steel sheet coated with a powder oftheprotective metal ispassed means for electrostatically applying a smallquantity of oil onto the surfaces of said rolls, said means forelectrostatically applying said oil comprising means for atomizing saidoil by means of primary and secondary pressurized air, a V nozzle forelectrostatically ejecting the atomized oil towards said mill rolls,means for varying the quantity of oil applied onto said rolls byadjusting the primary and secondary pressurized air, and means forconveying the atomized oil ejected from said nozzle towards said rollsof said rolling mill by the action of an electro static field, andequalizing rolls cooperating with said rolls of said rolling mill forforming thin films of said oil on the surfaces of said rolls of saidrolling mill. 2. The apparatus according to claim 1 which furthercomprises means for removing the powder of said metal from the surfacesof the rolls of said rolling mill.

3. The apparatus according to claim 1 wherein said equalizing rolls aremade of a material selected from the group consisting of felt, non-wovensynthetic fiber fabric and rubber.

4. The apparatus according to claim 1 wherein said means for atomizingsaid oil comprises a tank containing said oil, an atomizing nozzlecontained in said tank and supplied with pressurized air for atomizingsaid oil and means admitting secondary air into said tank for adjustingthe concentration of the atomized oil.

5. The apparatus according to claim 1 wherein said powder of protectivemetal is aluminum powder.

6. The apparatus according to claim 5 wherein said means forelectrostatically applying said small quantity of oil applies a quantityper unit area of said oil onto the surfaces of said rolls ranging from 5to 50mg/m 7. The apparatus according to claim 1 wherein said nozzlecomprises a double-walled nozzle.

8. The apparatus according to claim 1 wherein said means for varying thequantity of oil applied onto said rolls includes means for varying thesecondary air flow while maintaining the pressure of the primary oratomizing air at a predetermined value.

9. The apparatus according to claim 1 wherein said means forelectrostatically applying said small quantity of oil applies a quantityper unit area of said oil onto the surfaces of said rolls ranging from 5to SOmg/m".

1. Apparatus for manufacturing a steel sheet coated with a layer ofprotective metal comprising a rolling mill including: cooperating rollsbetween which a steel sheet coated with a powder of the protective metalis passed, means for electrostatically applying a small quantity of oilonto the surfaces of said rolls, said means for electrostaticallyapplying said oil comprising means for atomizing said oil by means ofprimary and secondary pressurized air, a nozzle for electrostaticallyejecting the atomized oil towards said mill rolls, means for varying thequantity of oil applied onto said rolls by adjusting the primary andsecondary pressurized air, and means for conveying the atomized oilejected from said nozzle towards said rolls of said rolling mill by theaction of an electrostatic field, and equalizing rolls cooperating withsaid rolls of said rolling mill for forming thin films of said oil onthe surfaces of said rolls of said rolling mill.
 2. The apparatusaccording to claim 1 which further comprises means for removing thepowder of said metal from the surfaces of the rolls of said rollingmill.
 3. The apparatus according to claim 1 wherein said equalizingrolls are made of a material selected from the group consisting of felt,non-woven synthetic fiber fabric and rubber.
 4. The apparatus accordingto claim 1 wherein said means for atomizing said oil comprises a tankcontaining said oil, an atomizing nozzle contained in said tank andsupplied with pressurized air for atomizing said oil and means admittingsecondary air into said tank for adjusting the concentration of theatomized oil.
 5. The apparatus according to claim 1 wherein said powderof protective metal is aluminum powder.
 6. The apparatus according toclaim 5 wherein said means for electrostatically applying said smallquantity of oil applies a quantity per unit area of said oil onto thesurfaces of said rolls ranging from 5 to 50mg/m2.
 7. The apparatusaccording to claim 1 wherein said nozzle comprises a double-wallednozzle.
 8. The apparatus according to claim 1 wherein said means forvarying the quantity of oil applied onto said rolls includes means forvarying the secondary air flow while maintaining the pressure of theprimary or atomizing air at a predetermined value.
 9. The apparatusaccording to claim 1 wherein said means for electrostatically applyingsaid small quantity of oil applies a quantity per unit area of said oilonto the surfaces of said rolls ranging from 5 to 50mg/m2.